Even if ACT's leader, John Banks, is not yet a dead man walking, his party surely is.

Mr Banks wrote the party's epitaph last week with his handling of questions over Kim Dotcom's donation to his mayoralty campaign.

It is an inglorious and shabby end. What must be particularly galling for ACT members is that the curtain has been brought down on them by an outsider who holds little love for the party.

Mr Banks is a true-blue National in ACT clothing, an accidental leader and unlikely candidate before he and his old mate, Don Brash, staged a reverse takeover in a doomed bid to help National.

For ACT there are now two choices. It can limp on until the next general election, ignoring its fate until National delivers the final coup de grace in Epsom, or it can give Mr Banks the boot and make him National's problem, call it quits on the tarnished ACT brand and disband, and hope someone of the calibre of Catherine Isaac might pull together a new right-wing party out of the ashes a year before the next election.

The second way offers a [faint] glimmer of hope as long as ACT moves swiftly to provide plenty of clear air for whoever picks up the right-wing banner.

The first way offers an even sorrier end than the one that is already staring ACT in the face. It also damages National.

That might not be a consideration now for ACT's members, who probably wish some of their misery on the bigger party, but eventually the prospect of a Labour-Greens government will galvanise them.

It might be the way of minor parties to believe, right up to the bitter end, that there is some way of turning their polling around, but a minor party has never looked more terminal than ACT looks right now.

The past few years have been a revolving door of scandals, in-fighting and internal turmoil.

If there is any consolation for Mr Banks, it is that the blame for its demise doesn't rest on his shoulders alone.

For National and Prime Minister John Key, there is no longer any profit in trying to keep the corpse breathing. Before the election, there was always the outside chance that ACT might bring three or four MPs into Parliament and shore up National's majority. In the end, ACT limped back in with just one MP, Mr Banks, despite Mr Key's largesse in gifting it Epsom with that infamous Newmarket cuppa.

Mr Key might be reluctant to cut Mr Banks loose right now but, come the campaign trail, National will only expose itself to headlines over "shabby deals" in Epsom, and be dragged through the mud over the Dotcom scandal by association, if it throws ACT another lifeline.

Getting rid of ACT, however, does not get rid of National's headache. It won't keep winning elections with close to 50 per cent support. The last election, in fact, was probably as good as it will get.

Unlike Labour, which in 1999 had the bulwark of the Alliance on its Left, and now the Greens, National's political allies – ACT, UnitedFuture and the Maori Party – are in their death throes.

The writing has been on the wall for ACT since Rodney Hide's leadership turned toxic, yet there do not appear to have been any credible efforts to establish a new right-wing brand.

In 2010, people started to talk about it, and a party at the famous farm of multimillionaire Alan Gibbs could even have kick-started it after it bought together leading lights from the Right. There was a lot of excitement about the prospect of starting up a new vehicle, but nothing came of it.

The move by Dr Brash and Mr Banks on the ACT party was a last roll of the dice after National became worried Mr Hide would lose Epsom. But they proved to be just as toxic to the ACT brand and, apart from a half-hearted Facebook campaign since, the steam seems to have gone out of any effort to set up a new vehicle.

There is no sign that anyone is ready to organise such a meeting. There are even fewer signs that a large number of voters is ready to assemble behind such a party.

The unpalatable choices facing National, then, are a deal with Colin Craig's hardline Christian Conservative Party, and hope it might make it into Parliament in numbers, although most National MPs would probably view that relationship as even more toxic than with ACT, or extending an olive branch to NZ First.

Given the alternatives, that must look attractive even if it would require an extraordinary volte-face from Mr Key. The groundwork could be laid now if National found some projects on which it could work constructively with NZ First over the next two years and point to a rehabilitated party and Winston Peters in 2014 as its excuse for leaving the door open.

For Mr Key, it is an ugly choice. It suited him to claim the moral high ground over Helen Clark in 2008 when Mr Peters was embroiled in his own donations scandal with Owen Glenn, a billionaire to rival Dotcom in his pursuit of revenge after being scorned.

But as he finds himself dancing on the same pin head as Ms Clark did in defence of Mr Peters, Mr Key might be wondering whether Mr Banks is writing his Government's epitaph as well.